It was just a few days ago that a group of scientists announced they had created the world’s first ‘synthetic’ mouse embryo made exclusively from stem cells – no sperm, egg or fertilization needed. That story’s place at the front of the “What could possibly go wrong?” file turned out to be very short – a new study has revealed that a different group of researchers has created baker’s yeast with human genes inserted inside of it. We know from the movie and Robert Thom’s (played by Charton Heston) famous cry: “Soylent Green is made out of people!” Will we soon be seeing ads for “’Duncan’ Donuts” baked with people yeast? Or India Pale ‘Al’ with real humans?
“What if we take the same group of genes that controls the sugar consumption and energy production of human muscles into yeast? Can we humanize such an essential and complex function in yeast?”
That is the seemingly innocuous question that sent biotechnologist Pascale Daran-Lapujade and her team at Delft University of Technology down the path that led to inserting human genes into yeast – the results of this research were published recently in the journal Cell. Daran-Lapujade saw this strange combination as a viable possibility, even though yeast lives as single cells and humans consist of a substantially more complex system because “the cells operate in a very similar way.” In her statement to Sci Tech Daily, Daran-Lapujade sounds in awe of – or perhaps in love with – the humble fungus.
“As compared to human cells or tissues, yeast is a fantastic organism for its simplicity to grow and its genetic accessibility: its DNA can be easily modified to address fundamental questions. Many pivotal discoveries such as the cell division cycle were elucidated thanks to yeast.”
This is not Daran-Lapujade first foray into the fungal world. She and a teach of researchers previously designed artificial chromosomes that operate as DNA platforms for building new functions into yeast. With that success, they decided to embark on actually adding human genes to yeast, create complete metabolic pathways, and see whether the cells could still operate as yeast – or whatever yeast with human genes is called. Beast? Ceased to be Yeast?
“We didn’t just transplant the human genes into yeast, we also removed the corresponding yeast genes and completely replaced them with the human muscle genes. You might think that you cannot exchange the yeast version with the human one, because it’s such a specific and tightly regulated process both in human and yeast cells. But it works like a charm!”
Daran-Lapujade led Ph.D. students and co-first authors Francine Boonekamp and Ewout Knibbe in what they described as a “surprisingly simple” quest to humanize yeast with human muscle genes. Before you ask … no humans were harmed in the making of this humanized yeast – the human muscle cells were lab grown. We know what you’re thinking (does the humanized yeast know too?) – why? Why give human genes to baker’s yeast? Stronger bread? Tougher donuts that don’t squirt jelly all over your lap when you bite in? Daran-Lapujade says the properties of human enzymes produced in yeast and in their native human cells are remarkably similar, so humanized yeast can now serve as a model for actual human cells. As expected, this is just the first step in a planned effort to add more human cells to yeast. Daran-Lapujade hopes that other researchers will benefit from her team’s new innovations in gene editing, while she and her focusing on engineering more humanized yeast.
“This is just the starting point. We can humanize yeast further and step by step build up a more complex human environment in yeast.”
What could possibly go wrong? Well, we’ve already alluded to the 1973 movie “Soylent Green” (which ironically is set in 2022) where a highly processed food product is found to be (spoiler alert) made from dead humans. We’ve also alluded to the fact that beer is made from yeast … brewer’s yeast comes from the same strains of yeast used to make bread and wine -- Saccharomyces cerevisiae. That brewer’s yeast is responsible for the fermentation that makes beer alcoholic by converting the sugars in barley into ethanol and carbon dioxide. Could humanized yeast be used to make beer … an India Pale ‘Al’ if you will? Why does this sound vaguely familiar?
“One human alcohol beer please.”
In the Season 2 Episode 6 of the mockumentary comedy horror show, “What We Do in the Shadows” entitled "On the Run," a vampire named Jim (played by Mark Hamill) sits down at a bar and orders a human alcohol beer. Could this be an allusion to a world where humanized yeast is made into beer? Of possibly another part of humans?
“The reason why we make this 'Pisner' beer is because we are a craft brewery out of Copenhagen and about four years ago we converted into organic, so all our beers are organic today. We thought it would be a great idea also to go into recyclable beer. So we want to test our brewers and test our opportunities to make recyclable beer."
What is Henrik Vang, chief executive of brewer Norrebro Bryghus, recycling to brew “Pisner” beer? If you haven’t figured it out from the name, the Danish brewery set up shop in 2017 at the Roskilde Festival, the largest music festival in Northern Europe, where it collected 50,000 liters of human urine, removed the phosphorous to be made into fertilzier, and used the cleaned remaining liquid to make beer – in other words, it put the P in Pisner. While it hasn’t caught on worldwide yet, it’s not because of the taste – festival goers who tried it said the beer tasted “really good” and was “fresh and full at the same time.”
Turning human genes into yeast into beer made with recycled urine while using the phosphorous to grow more barley to make more beer fits right into the closely-joined histories of humans and beer. Samples from stone mortars show that hunter-gatherers ground plants for fermentation 13,000 years ago, and the histories of most cultures around the world show evidence of beer being produced from whatever carbohydrates were available. That ancient beer was less of a recreational alcoholic beverage and more of a nutrient-filled food and a way of creating a relatively clean drinkable beverage to enable people to avoid drinking disease-filled water. In this way, yeast helped build strong humans. Now, humans are adding muscle genes to build strong yeast.
Will humanized yeast appreciate the human muscle genes? Or will it used this new strength to exact revenge for thousands of years of abuse?
What could possibly go wrong?
“Beer is made from people! It’s people!”